MONGOOSE, "$" Operator does't work as expected // elemMatch

Question

This is the command

const filter = {
    searchWord: req.body.searchWord,
    result: { $elemMatch: { idMeal: req.body.mealData.idMeal } },
};

const update = { $set: { 'result.$.strMeal': req.body.mealData.strMeal } };

const returnData = { returnOriginal: false };

Meal.findOneAndUpdate(
    filter,
    update,
    returnData,
    function (err, foundMeal) {
        res.json(foundMeal.result);
    }
);

If I use the $ operator it does not update the respective field but the 2nd field, so it works as if I typed

'result.1.strMeal'

Instead of

'result.$.strMeal'

Is this a Mongoose problem or what is it caused by?